1. Field of the Invention
The invention relates to a method of lining a pipe insulating shell, particularly one consisting of mineral fibres, with a foil comprising a coating of a heat activatable adhesive, and also to an apparatus suitable for carrying out the method.
2. Background of the Related Art
A method is known from DAS No. 24 16 471 in which a pipe insulating shell is lined by means of an apparatus comprising two parallel and adjacently disposed driveable rollers for supporting and rotating the pipe insulating shell. Diametrically opposite these rollers, there is also in this apparatus a pressing means adapted to be driven at the peripheral speed of the rollers and adapted for movement between a working position and a withdrawn loading and ejection position and intended for pressing the pipe insulating shell against the rollers, the foil being fed by feed means orientated transversely of the rollers. To activate the adhesive of the foil, it is furthermore intended that the roller adjacent the foil feed means be constructed as a heating roller.
Where this known apparatus is concerned, in operation a nonslit bare pipe insulating shell is pushed by a chain conveyor axially between the two rollers and the retracted pressing means, after which the pressing means is moved downwardly until it comes to bear against the pipe insulating shell. Afterwards, the pressing means, which is formed of revolving pressing belts, and the two rollers are separately driven so that the floatingly mounted pipe insulating shell is caused to rotate. At the same time, a previously prepared length of foil is introduced transversely and between the heated roller and the pipe insulating shell. As the foil slides over the heating roller, this latter is heated until the adhesive becomes capable of adhesion. At the same time, the foil is pressed by the heating roller against the heat insulating shell and is wound around it until such time as the pipe insulating shell has completed 11/4 revolutions. Lined in this way, once the pressing means has been disengaged again, the pipe insulating shell is then withdrawn axially out of the lining station by the already mentioned chain conveyor.
However, this known lining method is suitable only for nonslit pipe insulating shells, because these latter have a continuous outer surface which only has to be wrapped in the foil. An exact positioning of the pipe insulating shell in order to obtain an exact bearing of the foil against the edge of a longitudinal slit in the shell is not necessary in this case. Even if the foil, while it is being accommodated between the heating roller and the pipe insulating shell, is incorrectly entrained, i.e. does not bear in an exactly parallel position, or if there is a defective initial adhesion, then nevertheless an externally perfect product is obtained since the start of the foil is overlapped at the end by a portion of foil, the length of which corresponds to one quarter of a rotation of the pipe insulating shell. In addition, there is the relatively long stepwise operating time of this apparatus, since a lined shell cannot be removed until an unlined pipe insulating shell can again be pushed onto the rollers to be lined.